Flow restrictors, used for reducing pressure and regulating flow, are used in a vast number of different applications. For instance, CO2 insect traps, which produce CO2 from air and a combustible fuel, typically use two flow restrictors. A diaphragm regulator is first used to reduce the pressure of the combustible fuel from approximately 120 psi down to 11 in H2O (0.4 psi). However, such insect traps are very low pressure devices and require further pressure reduction. A second flow restrictor is used because the diaphragm regulator has poor reliability at pressures much below 11 in H2O. In order to further reduce the pressure, a fixed orifice may be used. When operating properly, the fixed orifice provides a very inexpensive means to accurately regulate pressure of the combustible fuel.
However, it is possible that precipitation will form on the orifice where there is a change in the pressure. The likelihood of precipitation is magnified by the abrupt disruption in the flow. Many orifices used for precise pressure drop applications are very small. They may be 10-thousandths of an inch or smaller. Due to the size of the orifice, even very small quantities of precipitate thereon can negatively impact the performance of the device. Further, if too much precipitate accumulates, the orifice can be blocked entirely, and the device may not operate. In the case of a CO2 insect trap, even relatively small changes in the overall flow rate can negatively impact performance of the device, by impacting the stochiometry of the reaction.
Thus, there is a need for a flow restrictor in such applications that effectively reduces fluid pressure without abrupt disruptions in the flow and without relying on a very small diameter orifice.